4 DefcTiption of a new VentUator^ 



with fo much avidity. Neither need I to mention that the nitrous acid m^de ufe of in the 

 receipt was equally capable of difengaging the fluoric acid, though we ufually make ufe of 

 the fulphuric. 



There remains, therefore, little doubt, that the art of etching on glafs does not 

 entirely belong to the moderns, or to deny that the ancients were altogether unacquainted 

 with it, would be doing them an injuftice. It feems rather, that this art belongs to the 

 difcoveries which were made in thofe times, in which men were little inclined to tranfmit 

 an account of their inventions to pofterity, and thus this art muft have been forgotten or 

 loft. ScTieele * difcovered the fluoric acid, and re-invented the art of etching on glafs in 

 the year 1771. But had Swanhard been able to purfue properly what either accident, or 

 ingenuity prefented to him, he might have enriched the arts, with a difcovery which ac- 

 quired great reputation to this Swedlfh philofopher one hundred years after. 



FREDERIC ACCUM. 



II. 



A Defcription of a new Injlrument'called the Blajl Ventilator. Invented hy J. W. Boswzii. 



I 



T would be fuperfluous to offer any arguments to the cultivators of natural philofophy, 

 refpefting the importance of any difcovery in that fcience. It is fufRcient to announce it 

 to thofe who fo well know, that no operation of nature is unimportant ; and that although 

 the firft perfon to whom a fa£l may occur, may not be able to point out all the advan- 

 tages which may arife from it, yet others of more difcernntent coming after him, may 

 improve upon his ideas, and perhaps ufe it for purpofes of much higher importance. 



What Dr. Hales has written of the great confequencc of the fubje£l of ventilation to 

 health, and the prefervation of the food of man, renders it unnecefTary to expatiate on the 

 importance of any new difcovery in this art; and to his excellent treatife on this matter, I 

 beg leave to refer thofe who have any doubts on the advantages arifing from it. 



The method of forcing air in any required direftion, by a fall of water pafling from a 

 fmaller into a larger tube, in an engine called the f Water Blaft, is now well known, and 

 frequently applied in mines and furnaces with great eflScScy. 



Some confiderations on this machine led me to conjedlure long fince, that a current of 

 air might be made to aft inftead of a fall of water, in an apparatus conftrufted on princi- 

 ples fomewhat fimilar to the above, and thus applied fo as to draw off foul air or fmoke 

 from any places required, in fituations where the other could not be ufed. It was only 

 lately that I have been able to think of any method of putting this matter to the teft of ex- 



• Tianfaftions of the Swedifl; Academy for the year 1771. C. xxxiii. p. iji. 

 f Dr. Lewis, in his very ufeful work on the Arts, has laid down the beft conftruftion of this engine, 

 from a6\ua! experiment. 



perimentj. 



